Whilst LW is CLOSED, delete the LW preferences folder but first move out the Downloads.dat file to a different location. Then open LW up again, close it again. Then replace the new downloads.dat file with the old one. This will ensure your old downloads history is retained. Deleting LW Preferences folder in OSX.
LW 5 has the ability to find fresh people to connect with much better than LW 4 did. BTW if you use your OSX firewall, remove the old LW listing & add the newer LW to it.
OSX Firewall settings for Leopard